var tbody=document.getElementById('body');
var trs=tbody.getElementsByTagName('tr');
function over(){
	for (var i=0;i<trs.length;i++) {
		if (i%2==0) {
			trs[i].style.background='lightskyblue';
		}else{
			trs[i].style.background='palevioletred';
		}
	}
}
function leave(){
	for (var i=0;i<trs.length;i++) {
		trs[i].style.background='';
	}
}
